Concatenate regexes prio to compilation

* Concatenating regexes into one Pattern might yield better performance under (un)certain conditions.
* Filenames are tested against regexes with no os.sep in them. This may or may not be what we want to do.
And alternative would be to test against the whole (absolute) path of each file, which would filter more agressively.

qt/exclude_list_dialog.py

@@ -68,10 +68,13 @@ class ExcludeListDialog(QDialog):
         gridlayout.addItem(QSpacerItem(0, 0, QSizePolicy.Minimum, QSizePolicy.Expanding), 4, 1)
         gridlayout.addWidget(self.buttonClose, 5, 1)
         layout.addLayout(gridlayout)
+        self.linedit.setPlaceholderText("Type a regular expression here...")
+        self.linedit.setFocus()
 
     # --- model --> view
     def show(self):
         super().show()
+        self.linedit.setFocus()
 
     @pyqtSlot()
     def addStringFromLineEdit(self):